J.A. Woollam M-2000, Hardware Manual

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54 ©2023 J.A. Woollam Co. M-2000® Hardware Manual
System Alignment
System alignment is the adjustment of the Light source and Receiver
components relative to the base of the M-2000 system (in the “straight-through”
configuration). The straight-through configuration is when the angle of
incidence is set at 90°; the beam of light will directly enter the receiver (the
sample is not needed in this case). It also refers to the "Lookdown" detector
alignment for the Auto Tip/Tilt option. It is required when the system is first
delivered, when first mounting the system onto the base, or whenever the
integrity of the alignment is in question.
Alignment with Filter Wheel Option
When performing the system alignment using a filter wheel, there are some
factors to consider. Since the straight-through position is included in the
calibration, the signal needs to be optimized throughout the entire spectrum. If
a higher density filter is selected, the DUV signal is lower with respect to the
overall average signal. As shown in Figure 4-4 and Figure 4-5, if a lower density
filter is selected and the iris(es) or filter position on the Receiver unit is closed
down to avoid ‘Overload’, the DUV signal is optimized. This results in a much
better calibration result at these lower wavelengths. This procedure also applies
to sample alignment for highly reflective samples (ex: Silicon wafer).
Examples of Source ND filter wheel positions vs. Signal Intensity:
Figure 4-4. Filter position 6 with iris open.